"Mark has the credibility to say, 'I'm going to spend $19 billion to buy something that has essentially no revenue model'. I think his aggressiveness is wise - although the price is higher than I would have expected. It shows that user bases are extremely valuable."

"We're both Harvard dropouts, we both had strong, stubborn views of what software could do. I give him more credit for shaping the user interface of his product," he explained.

"He's more of a product manager than I was. I'm more of a coder, down in the bowels and the architecture, than he is. But, you know, that's not that major of a difference. I start with architecture, and Mark starts with products, and Steve Jobs started with aesthetics."